Lifting tongs



July 15, 1959. D. J. MORO 3,455,593

LIFTING TONGS Filed Sept. 28, 1966 3 Sheets-Sheet 1 FIG. 3

INVENTOR Dominik J. Moro ATTORNEYS July 15, 1969 D. J, MORO `3,455,593

LIFTING TONGS Filed Sept. 28, 1966 5 Sheets-Sheet 2 Nlnllws rl @by amel #dans ATTORNEYS r MO T M N. ETV V N .bln T .m m O D BY Email, emmls, Mom,

July l5, 1969 D. J. MORO LIFTING TONGS Filed Sept. 28. 1966 3 Sheets-Sheet 3 35 `\.l.. "33 34 Jass 36 J so \54 s3 J k s2 INVENTOR Dominik J. Moro Pamuk dmords, 31%.@ or wddams ATTORN EYS United States Patent U.S. Cl. 294-110 6 Claims ABSTRACT F THE DISCLOSURE A lifting tongs includes grappling arms secured to a first support member, link arms secured to -a second support member and to the upper ends of the respective grappling arms, and a clevis secured to the second support member. An improved locking means in combinatlon therewith includes a hinge plate secured to the second support member and having a carn rotatably mounted thereon. A hinge plate guide mounted on the first support member slidably receives the hinge plate and has an opening in one side to receive the cam in locking engagement. A cam stop mounted in the lower portion of the hinge plate guide displaces the cam into engaging position with the guide opening.

This invention relates to lifting tongs of the type used to lift heavy objects such as ingots or billets. More particularly, this invention relates to a novel means for automatically locking the jaws of the lifting tongs in an open position until it is desired to grapple the object to be lifted.

It is normally required that a workman on the iloor assist the crane operator in the use of lifting tongs. The :oorman has the job of manually locking the tongs in an open position until they are maneuvered into engaging relationship with the load and then of releasing the lock to allow the tongs to grapple the load. The job of the floorman is a dangerous one and serious injuries are not uncommon. Efforts have been made in the past to provide tongs with automatic locking means but all known automatic locks 4are either unreliable or so complex as to break down frequently. The lifting tongs of the present invention has none of these disadvantages; it is reliable, of simple construction and may be manufactured economically.

The lifting tongs of the present invention is of the type which has a rst support member and first and second grappling arms secured to the rst support member; the lower ends of the grappling arms deline cooperating jaws. First and second link arms are secured to a second support member and to the upper ends of the grappling arms. A clevis is also secured to the second support member. A hinge plate having a cam rotatably mounted thereon is secured to the second support member and is slidably received in a hinge plate guide which is mounted on the first support member. The hinge plate guide has an opening in one of its sides, which opening receives the cam in locking engagement. A cam stop is mounted in the lower portion of the hinge plate guide to displace the cam into position to engage the guide opening.

As noted above, the present lifting tongs has the particularly desirable advantage of eliminating the need for a floorman to work in conjunction -With the crane operator. Furthermore, since the present locking means are reliable and durable, downtime is significantly reduced with a corresponding gain in efficiency. Finally, in contrast with many of the previous tongs, the locking means of the present invention in no way restricts the range of sizes of articles which may be grappled.

A preferred embodiment of the invention is described hereinbelow with reference to the drawings wherein:

3,455,593 Patented July 15, 1969 e ICC FIG. l is a front elevation of a lirst embodiment of the tongs of the present invention;

FIG. 2 is a front elevation of a second embodiment of the tongs of the present invention;

FIG. 3 is a side elevation of the tongs of FIG. 2;

FIG. 4 is a front elevation of a third embodiment of the tongs of the present invention;

FIGS. 5(11) to 5 (d) are enlarged views of the locking mechanism of the tongs of FIG. 4 showing various positions of the components in operation; and

FIG. 6 is a partial sectional view of the cam and hinge plate guide of the tongs of the present invention taken through line `6 6 of FIG. 4.

A description of the construction of the present tongs is best achieved by particular reference to the specific embodiment of FIG. 4, bearing in mind that the principles of the invention are identical for the embodiments of FIGS. l and 2 as well. Like reference numerals are applied to like parts in the different embodiments of FIGS. l-6, with the numerals followed by the suffix prime in FIG. 1 and the suffix double prime in FIGS. 2 and 3.

The tongs 10 of the present invention comprises a first support 11 (which may be a pivot pin as in FIG. 1 or a frame bar as in FIGS. 2 to 4) and a pair of grappling arms 12, 13 secured to the rfirst support 11. The connection between the rst support 11 and the grappling arms 12, 13 may be slidable as in FIG. 4 or pivotal as in FIGS. 1, 2 and 3, depending upon the specific requrements in each case. A pair of link arms 14, 15 are pivotally secured at one end to the grappling arms by pins 16, 17 and are pivotally secured at the other end to a second support member 18 which in the embodiments shown in FIGS. l (at 18') and 4 is a pivot pin. A clevis 19 is also secured to the second support member 18. When in use a crane or derrick (not shown) supports the tongs by securing its lifting cable to the clevis 19.

The locking means of the present invention comprises a hinge plate 20 secured to the second support member 18. In the embodiments of FIGS. 1 and 4, the hinge plate is generally rectangular in shape and depends downwardly from the second support. A cam 30 is rotatably mounted on the hinge plate 20` as shown in FIG. 4. The cam is four sided, its longer opposing marginal sides 31, 32 being parallel to one another and of equal length but its shorter opposing marginal sides 33, 34 defining concave surfaces. The portions of cam 30 where the parallel sides 31, 32 meet the concave sides 33, 34 dene four cam lobes `'3S-38. The cam 30 is mounted at the lower portion of the hinge plate 20 eccentrically with respect to the vertical axis of the hinge plate 20. However, the position of the cam 30 with respect to the hinge plate 20 must be such that when the cam 30 is at the orientation shown in FIG. 5(a), its longer side 32 will not overlap the side of the hinge plate 20. A spring washer 40 shown best in FIG. 6 is mounted coaxially with cam 30; the washer 40y exerts a force against the cam 30 which tends to restrain its rotation. As a result, cam 30 will rotate only under an applied torque and will remain in a given orientation until so torqued. A hinge plate guide 50 is mounted on the first support member 11. The guide 50 has parallel vertical sides 51, 52, a base 53 and is so dimensioned as to slidably receive the hinge plate 20. The vertical side 52 has an opening S4 which may receive the cam 30 in locking engagement in a manner to be described hereafter. A cam stop 60` is mounted on the base 53 of the guide 50 midway between the vertical sides in line with the vertical axis of hinge plate 20` and in the path of travel of cam 30j. The construction of the hinge plate guide is the same in the embodiments shown in FIGS. 1 and 4.

The locking means of the FIGS. 2 and 3 embodiment differs slightly in appearance from that of FIGS. 1 and 4 but the principles of operation are identical. Referring specifically to FIGS. 2 and 3, the hinge plate 20 is fixedly secured to the second support member 18". Cam 30" is rotatably mounted on the hinge plate 20" as in the other embodiments. Since the hinge plate 20" is iixedly secured to the second support 18" the hinge plate guide, here designated 70, is not provided with vertical sides to restrain the travel of the hinge plate 20". The hinge plate guide 70 is secured to first support 11; it has a cut-out section 71 which corresponds to opening 54 and 54 of the FIGS. 1 and 4 embodiments and upwardly projecting portion 72 which corresponds to cam stop 60.

For purposes of illustration, the operation of the FIG. 4 embodiment will be explained in detail with reference to FIGS. 5(a) to 5(d).

FIG. 5(a) illustrates the relative position of the hinge plate 20 and hinge plate guide 50 at the outset of an operation. In this position, the tongs are suspended above the floor and the grappling arms 12, 13 are in a closed position. The longer marginal sides 31, 32 of cam 30 are vertically oriented. To set the locking means, the crane operator lowers the tongs 10 to the iioor where the grappling arms 12, 13 are forced apart by the weight of tongs 10 and the hinge plate 20 begins to move downwardly in the guide 50.

As the grappling arms 12, 13 spread completely apart the concave side 34 of cam 30 forcibly abuts cam stop 60 causing the cam 30 to rotate into the position shown in FIG. 5(b). In this position, cam lobe 38 protrudes into opening 54.

The crane operator now lifts the tongs 10l once again and as the grappling arms 12, 13 close, hinge plate 20 moves upwardly in guide 50 until concave surface 33 of cam 30 comes into contact with the upper periphery of opening 54 causing rotation of cam 30 until cam lobe 37 abuts vertical wall 52 as shown in FIG. 5(0). Further rotation of cam 30 is prevented because hinge plate 20 is restrained by vertical wall 51. Hinge plate is thus restrained from further upward movement in guide 50 and accordingly grappling arms 12, 13 are locked in an open position.

The tongs 10 are then lowered onto the load to be grappled; and as the tongs contact the load the grappling arms 12, 13 open slightly and the hinge plate 20 moves downwardly in guide 50 until side 32 of cam 30 contacts cam stop 60 causing cam 30 to rotate into the position shown in FIG. 5(d).

The cycle is completed as the tongs 10 are lifted and grappling arms 12, 13 close to grip the load. Hinge plate 20 moves upwardly in guide 50 and side 31 of cam 30 forcibly contacts the upper periphery of opening 54 causing cam 30 to rotate into the orientation illustrated in FIG. 5(11).

I claim:

1. In a lifting tongs of the type having a first support member, `first and second grappling arms secured to the first support member the lower ends of which grappling arms define cooperating jaws, a second support member, first and second link arms secured to the second support member and to the first and second grappling arms respectively at the upper ends of the grappling arms, and a clevis secured to the second support member, the improvement in combination therewith comprising:

(a) a hinge plate secured to the second support member,

(b) a cam rotatably mounted on the hinge plate,

(c) biasing means for restraining the cam from rotation and for maintaining it in a given orientation with respect to the hinge plate until it is acted upon by an applied force,

(d) a hinge plate guide mounted on the first support member slidably receiving the hinge plate and having an opening in one side thereof to receive the cam in locking engagement, and

(e) a cam stop mounted in the lower portion of the hinge plate guide to displace the cam into position to engage the guide opening as the hinge plate translates downwardly in the hinge plate guide.

2. A lifting tongs according to claim 1 wherein the means for maintaining the cam in a given orientation with respect to the hinge plate comprises a spring washer mounted coaxially with the cam.

3. A lifting tongs as in claim 1 wherein the cam is four sided, two marginal sides of which cam are parallel and of equal length and the other two marginal sides of which cam are concave.

4. A lifting tongs as in claim 3 wherein the parallel marginal sides are longer than the concave marginal sides.

5. In a lifting tongs of the type having a first support member, rst and second grappling arms secured to the first support member the lower ends of which grappling arms define cooperating jaws, a second support member, first and second link arms secured to the second support member and to the first and second grappling arms respectively at the upper ends of the grappling arms, and a clevis secured to the second support member, this improvement in combination therewith comprising;

(al)y a hinge plate secured to the second support mem- (b) a cam rotatably mounted on the hinge plate eccentrically with respect to the vertical axis thereof,

(c) means for maintaining the cam in a given orientation with respect to the hinge plate until the cam is acted upon by an applied force,

(d) a hinge plate guide mounted on the first support member slidably receiving the hinge plate and having an opening in one side thereof to receive the cam in locking engagement, and

(e) a cam stop mounted in the lower portion of the hinge plate guide to displace the cam into position to engage the guide opening as the hinge plate translates downwardly in the hinge plate guide, said cam stop being mounted eccentrically inwardly towards the vertical axis of the hinge plate guide with respect to a vertical line passing through the center of rotation of the cam.

6. A lifting tongs as in claim 5 wherein the cam stop is mounted substantially in line with the vertical axis of the hinge plate guide.

References Cited UNITED STATES PATENTS 2,629,627 2/1953 Stone 294--110 3,155,416 1l/1964 Buchik et al 294-1l0 X ANDRES H. NIELSEN, Primary Examiner 

